with t1 as ( select u.device_id, q.question_id, q.result from user_profile as u right join question_practice_detail as q on u.device_id = q.device_id where university = '浙江大学' order by u.device_id, question_id ) select qd.difficult_level, sum(if (result = 'right', 1, 0)) / count(1) as correct_rate f...